When an intercontinental ballistic missile (ICBM) is launched into an orbit toward a target, it can be readily detected by radar as it approaches a target area. Several decoy missiles, which are designed to appear to a radar system as though they are ICBM's, may accompany one or more ICBM's so that a cluster of missiles will appear to a tracking radar, thereby camouflaging the identity of the true ICBM's. However, this cluster of missiles is also being observed by detection systems other than radar. For example, passive infrared detection systems such as forward looking infrared systems (FLIRS) in the 3-5 micron band and the 8-14 micron band are used. These systems sense the temperature of an object by observing the thermal energy which it radiates. Thus, when an ICBM and accompanying decoys are launched into a polar orbit they will pass from a sun lit region into a region shaded by the earth's shadow. When this happens, both the massive ICBM's and any decoys which accompany them begin to radiate energy to the cold regions of outer space and begin to cool down. Since each radiates energy at about the same rate, the ICBM's with their large thermal mass tend to change temperature very slowly. However, the light weight decoys, because of their small thermal mass, change temperature very rapidly by comparison, allowing the FLIRS to quickly discriminate between the ICBM's and the decoys.